Jack terminal for spark-plug lead



April 5, 1955 J. w. ANDERSON ETAL 2,705,786

JACK TERMINAL FOR SPARK-PLUG LEAD Filed May 20, 1952 Y 2 Sheets-Sheet l John H/Inderson BY Oscar [17655 E W HTWRNEY.

April 5, 1955 J.'w. ANDERSON ET AL 2,705,786

JACK TERMINAL FOR SPARK-PLUG LEAD 2 Sheets-Sheet 2 Filed May 20, 1952 United States Patent Ofl ice 2 ,705,786 Patented Apr. 5, 1955 JACK TERMINAL FOR SPARK-PLUG LEAD John W. Anderson, Westfield, and Oscar Kress, Staten Island, N. Y., assignors to Airtron, Inc., Linden, N. J., a corporation of New Jersey Application May 20, 1952, Serial No. 288,896

4 Claims. (Cl. 339213) The present invention relates to improved means for connecting a wire lead to a spark-plug and is directed more particularly to simple, yet highly effective means for holding an insulating sleeve securely in position upon a jack which is connected to such a wire.

Prior spark-plug leads for high tension systems such as were used for a time on jet engines have commonly employed a helical spring at one end of the lead wire adapted to be held with its free end seated upon a button associated with the spark-plugs central electrode. This arrangement, however, is not satisfactory for carrying the high instantaneous current which is now being employed in jet engine ignition systems. These new ignition systems employ electrical energy which is instantaneously released from a capacitor at high voltage. Jack terminals according to the present invention carry such high instantaneous current satisfactorily while the prior spring type leads have failed.

Accordingly, it is an important object of this invention to provide an improved jack terminal for a sparkplug lead which will function satisfactorily in present high instantaneous current ignition systems.

Another important object is to provide such a jack terminal which has very few parts, which may be easily assembled and which cannot accidentally become disassembled.

Another important object is the provision of such a jack terminal in which an insulating sleeve cooperates with other parts of the terminal to hold them together against becoming accidentally disassembled.

The foregoing and other objects are accomplished according to the present invention of which a single embodiment is shown in the accompanying drawings for illustrative purposes without, however, limiting the invention to that particular embodiment.

In the drawings:

Figure 1 is a view of a jack terminal, according to this invention, in axial alignment with a spark-plug with which it may be associated, the upper half of the figure being partially broken away and partially in section to show details, and the lower half of the figure being in side elevat-ion.

Fig. 2 is a view somewhat similar to Fig.1, but showing the jack terminal and the spark-plug in their interconnected relationship.

Fig. 3 is an enlarged view of the jack terminal shown in Figs. 1 and 2, this figure likewise being in section and partly broken away in the upper half thereof and being in side elevation in the lower half thereof.

Fig. 4 is a cross-sectional view of the jack terminal substantially on the line 4-4 of Fig. 3.

Fig. 5 is a central, longitudinal, sectional view of the iack terminal showing certain parts thereof in initial positions which they occupy during the assembly of the terminal.

Fig. 6 is a view somewhat similar to Fig. 5, but showing the parts of the jack terminal at an intermediate point in the assembly thereof; and

Fig. 7 is a cross-sectional view of the partially assembled jack terminal substantially on the line 77 of Fig. 6.

The illustrated jack terminal 9 comprises a more or less tubular jack 10 of electrically conductive metal formed at its inner end with an axial bore 12 for receiving therewithin the stripped end 14 of an ignition wire 16. The jack is also provided with a side opening 18 through which solder may be introduced into the bore 12 and about the stripped end 14 within the bore to interconnect, with a highly efiicient electrical connection, the wire 16 and the jack 10.

The outer end of the jack 10 is formed with longitudinal slots 20 which give the outer end of the jack the character of a plurality of circumferentially arranged fingers 22, each of which is inwardly beveled at its free end, as at 24, to facilitate the entry, axially, into the jack and between said fingers, of a central contact pin 26 in a spark-plug 27 to which the jack is to be connected.

Although the jack is preferably formed of somewhat resilient metal so that the fingers 22 will have some inherent resiliency and function as spring fingers, nevertheless, it is preferred to provide supplemental means for urging the fingers 22 yieldably into and maintaining them in very tight contact with the pin 26; and, for this purpose, said fingers, considered collectively, are formed with an outer annular recess 28, and a contractile coil spring 30 is arranged in encircling relationship to the fingers 22 and seated within said recess. The spring 30, preferably, is of such normal inside diameter that, when it is in its described position encircling the fingers 22, it exerts at least a slight contractile force thereon. The wire of which the coil spring 30 is formed, preferably, is of lesser diameter than the depth of the recess 28, so that, when the spring is in its described position about the fingers 22, it will not protrude radially beyond the outside surfaces of said fingers.

In assembling a jack terminal according to this invention, the stripped end 14 of the wire 16 is first soldered into the bore 12 of the jack. Then an insulating sleeve 32 is slid axially upon the jack 1i) and the adjacent end portion of the wire 16, this being done from the outer or free end of said jack. This sleeve, preferably, is formed of dielectric material which is somewhat resilient for a purpose which will hereinafter be made clear. It has been found that a very suitable substance for use as such an insulating sleeve is a molded polymer of tetrafluoroethylene, which is available under the trade name Teflon. The molded sleeve 32 is formed with an internal abutment which may be in the form of an inwardly extending annular flange or shoulder 34, and the jack 10 is preferably formed with an outer annular flange or shoulder 36, the outside diameter of the shoulder being greater than the inside diameter of the shoulder When the sleeve 32 is slid onto the jack 10 and the adjacent end portion of the wire 16, such movement of the sleeve leftwardly (as viewed in the drawings) is limited by the shoulder 34 of the sleeve coming into contact with the flange 36 on the jack. When the sleeve reaches its extreme leftward position as thus limited, the jack and the sleeve would be approximately in their relative positions shown in Figs. 2, 3, 5 and 6. In that condition, however, there is nothing to prevent the sleeve from sliding 0d the jack with a reverse or rightward movement.

Means are, accordingly, provided for locking the sleevein its assembled association with the jack, which means include a locking collar 38 which, preferably, is formed of somewhat resilient metal or other suitable resilient material. The outer or right end of this collar has a cylindrical portion 40 and a radial flange 42 extending outwardly from the outer end of said cylindrical portion, and a circumferential series of spring fingers 44, which are integral at their base ends with the cylindrical portion 40 of the locking collar, extend leftwardly and are formed at their free ends with inturned flanges or hooks 46 which enter into locking engagement with a preferably hookshaped annular shoulder 48 formed on the exterior of the jack 10. To the left of shoulder 48, as viewed in Figs.

3, 5 and 6 and partially defined thereby, is the external annular recess 49 of jack 10, in which books 46 are located after assembly of the parts.

The cylindrical portion 40 and the fingers 44 of the locking collar are relatively thin and normally fit quite closely between the outer surface of the jack 10 and the adjacent inner surface of the insulating sleeve 32; and the flange 42, when the finger ends 46 of the locking collar are in permanent locking position as they appear in Fig. 3, extends into axial alignment with the adjacent radial end surface 43 of the insulating sleeve, thereby constituting an abutment which positively prevents said sleeve from moving rightwardly relatively to the jack and the wire which is soldered thereto.

The locking collar 38 is incorporated with the other parts of the jack and insulating sleeve assembly in a manner best understood from Figs. 5, 6 and 3. After the sleeve has been pushed leftwardly into place as it appears in Fig. 5, the locking collar 38 is pressed leftwardly, to bring the free ends of the fingers 44 and, more particularly, the hooks 46 thereon, into an initial telescoping position between the right end of the jack 10 and the corresponding adjacent end of the insulating sleeve 32. Although the radial dimension of the hooks 46 is greater than the normal annular space 45 between the jack and the insulating sleeve, and in which fingers 44 or located when assembled nevertheless, the said sleeve, being of Teflon or other suitable, somewhat resilient material, permits the locking collar 38 to be pushed forcibly leftwardly; the insulating sleeve meanwhile expanding to some extent to accommodate the books 46 between said sleeve and the jack.

Fig. 6 shows the approximate position of the locking collar 38 and, more particularly, the hooks 46 thereof relatively to the yielding insulating sleeve and the jack at an intermediate point in the insertion of said collar. Further leftward movement of the locking collar, in response to the pushing force applied thereto, finally terminates when the flange 42 of said collar abuts the end of the insulating sleeve. At that point, the hooks 46 are in position to snap radially inwardly into locking association with the shoulder 48 on the jack. This inward snapping movement of said hooks results partly from the fact that the fingers 44 of the locking collar are somewhat resilient and partly from the fact that the resilient insulating sleeve continuously tends very strongly to contract, thereby aiding in the inward movement of the hooks 46 when the latter are clear of the shoulder 48.

While the resiliency of the fingers 44 alone may suffice to establish and maintain the hooks 46 in firm locking association with the shoulder 48 on the jack, nevertheless, the insulating sleeve, by again assuming its normal cylindrical shape after the hooks 46 snap into locking position, constitutes a relatively strong contractile means effectively preventing the hooks 46 from becoming disengaged from the shoulder 48. In this way, the locking collar 38 serves as a very positive means for preventlng the jack and insulating sleeve assembly from becoming unintentionally disassembled.

A jack terminal according to this invention, as hereinbefore described, is associated with the spark-plug 27 merely by being pushed axially into a ceramic insulating sleeve 50 thereof until a flat annular surface of an outer shoulder 52 on the insulating sleeve 32 seats upon flat, annular, outer end 54 of said ceramic sleeve. When the parts are thus associated, the fingers 22 of the jack 10 firmly embrace the spark-plugs central contact pin 26 to effect a firm electrical connection therewith. The firmness of this connection is assured not only because of the resiliency of the fingers 22, but also because of the contractile force applied to said fingers by the coil spring 30.

Means ordinarily would be associated with the insulating sleeve 32 for holding the jack and said sleeve against dislodgment from the spark-plug. Such means may, for illustration, comprise a union nut 56 which threads upon an outer threaded end portion 58 of the outer metal shell of the spark-plug, the nut 56 being provided with an inturned annular flange 60 which engages a shoulder 62 of a follower ring 64 which slidably surrounds the sleeve 32. The follower ring 64, in response to tightening of the nut 56, compresses a coil spring 68 axially between the follower ring and a washer 70 which, in turn, presses against an exterior shoulder 72 formed on the insulating sleeve 32. The latter shoulder faces oppositely to the shoulder 52 so that the compressive force of the spring 68 holds the jack assembly firmly in place with the shoulder 52 resting upon the end surface 54 of the ceramic insulating sleeve of the sparkplug. The spring 68 preferably is connected to the follower by having an end coil portion 69 thereof held within a partial spiral groove 65 in said follower in a well understood manner.

On some occasions, when it is desired to disconnect the jack assembly from the spark-plug, considerable force may be required to pull said assembly from within the plug after the union nut 56 has been disconnected. To facilitate pulling of the jack assembly from the sparkplug, without involving a pull directly upon the wire 16 (which might disturb the latters soldered connection to the tubular jack 10), an expansible, split snap ring 76 is seated within an internal, annular groove 78 formed in the follower ring 64. This snap ring is only very slightly narrower than said groove and, in its contracted condition, as shown in Figs. 1 and 2, it is of such outer diameter that it may expand slightly in the groove 78 and of such inner diameter that it seats within an external, annular groove 80 formed in the insulating sleeve 32. I

The left end of the sleeve 32 preferably is externally beveled as at 82 to expand the snap ring 76 and permit the follower ring 64 to be pushed endwisely onto the left end of the sleeve 32 during the assembly of the parts of this device. When the follower ring, in said assembling operation, reaches its position indicated-in Fig. 1, the snap ring 76, being positioned directly opposite to the groove 80, is free to contract into said groove. The snap ring is of such radial thickness that, when thus contracted, it simultaneously extends into both grooves 78 and 80. The groove 80 is sufiiciently wide to permit the snap ring 76 to slide axially therein when the union nut 56 is tightened as in Fig. 2.

When it is desired to disconnect the jack assembly from the spark-plug, the union nut 56 is uncoupled and slid leftwardly onto the wire 16. This uncovers the shoulder 62 of the follower ring, and this shoulder affords a handhold for one wishing to pull the jack assembly from the spark-plug. When one thus exerts a pull on the follower ring, the snap ring 76, being in locking engagement with both the follower ring and the insulating sleeve 32, constrains the latter and the entire jack assembly to withdraw from the spark-plug To minimize the tendency of electrical energy to leak from the connection between the jack 10 and the contact pin 26, a dielectric paste or jelly is preferably applied to the end surface 54 of the ceramic sleeve 50 and/or to the shoulder 52 of the sleeve 32 which contacts said end surface when the jack is in complete connected association with the spark-plug.

A jack terminal arrangement such as has been hereinbefore described as one of various possible embodiments of this invention is highly etficient in conducting high instantaneous current without material leakage. It is very simple and consists of relatively few, inexpensive parts. It is very easily assembled, and, once assembled, it is practically impossible for it to become disassembled unintentionally. Also, it is of such character that it can be very quickly locked in place in connected association with a spark-plug.

Although only a single embodiment of the invention has been illustrated and described herein to give an understanding of the present inventive principles, it should, nevertheless, be understood that those principles may be utilized in variousother ways without, however, departing from the invention as set forth in the following claims.

What we claim is:

l. A connection terminal for connecting an electric wire to a related electrical device, comprising a contact element having a contact portion at one end thereof for engaging a contact in such related device, a wire-receiving portion toward the other end thereof for fixedlyattaching such a wire thereto, an annular, radially outwardly extending abutment flange, and being formed with an external annular recess; a sleeve of resilient, insulating material extending about said contact element with a narrow annular space therebetween and having an inner annular shoulder in abutting relationship with said abutment flange to limit axial movement of said sleeve toward the contact elements said other end; and a locking collar encircling said contact element and having a flange extending radially outwardly at one end thereof into abutting relationship with an adjacent end surface of the insulating sleeve to oppose axial movement of the latter toward the contact elements said one end, and plural fingers connected integrally to said flange, and extending axially within the said narrow annular space, and having inturned ends extending within said external annular recess to oppose axial movement of said collar relatively to said sleeve and contact element, the said inturned ends being of greater radial dimension than said narrow annular space, but the resiliency of said sleeve being suificient to enable the sleeve to expand during assembly of the terminal to permit the said finger ends to be moved axially through said space and to contract when said finger ends are in radial alignment with said external annular recess; the sleeve, when thus contracted, closely encircling said finger ends whereby to oppose their dislodgement from said external annular recess.

2. A jack terminal comprising a tubular jack having a yieldable, contact-pin-embracing portion toward one end thereof, a wire-receiving portion toward its other end, and a radially outwardly extending abutment; an insulating sleeve extending about said jack and having a radially inwardly extending abutment in abutting relationship with the said jacks abutment to limit axial movement of the said sleeve toward the jacks said other end; and a locking collar telescopically extending between the pin-embracing portion of the jack and a surrounding portion of said sleeve and coacting with said jack and sleeve to lock the latter against axial movement toward the jacks said one end; said locking collar having a flange extending radially outwardly from one end thereof into abutting relationship with an adjacent end of the insulating sleeve and plural resilient fingers extending axially at the other end of said collar and having radially inturned ends abutting adjacent radial surfaces of the jack which face oppositely to the mentioned end of the insulating sleeve.

3. A jack terminal comprising a tubular jack having a yieldable, contact-pin-embracing portion toward one end thereof, a wire-receiving portion toward its other end, and a radially outwardly extending abutment; an insulating sleeve extending about said jack'and having a radially inwardly extending abutment in abutting relationship with the said jacks abutment to limit axial movement of the said sleeve toward the jacks said other end; and a locking collar telescopically extending between the pin-embracing portion of the jack and a surrounding portion of said sleeve and coacting with said jack and sleeve to lock the latter against axial movement toward the jacks said one end; said jack having an outer, annular recess and the said locking collar having an axially extending hookend finger, the hook end of which, when the device is assembled, extends radially into said recess and constitutes an abutment opposing axial movement of said collar toward the jacks said one end and an outwardly extending radial flange on said collar, the said flange and said abutment of the jack being in abutment with oppositely axially facing surfaces of said sleeve whereby to hold the latter against material endwise movement relatively to the jack.

4. An elongate jack terminal comprising a tubular jack, an insulating sleeve and a locking collar, said jack having a yieldable, contact-pin-embracing portion at one end thereof, said portion further having an external shoulder facing the other end of said jack, said portion further having an external annular recess adjacent to and partially defined by said shoulder, said jack further having a wire-receiving portion at the other end thereof, and a radially outwardly extending abutment, said insulating sleeve extending about said jack and having a radially inwardly extending abutment in abutting relationship with the said jacks abutment to limit axial movement of the said sleeve toward the jacks said other end, and said locking collar extending telescopically between said pinembracing portion and said sleeve and having a radially outwardly extending flange at one end, said flange abutting a radial end surface of said sleeve, said collar further having plural, axially extending resilient fingers at its other end, said fingers having radially inturned ends, said ends extending into said recess and abutting said shoulder to prevent motion of said collar toward said one end of said jack, said flange of said collar thereby further limiting motion of said sleeve toward said one end of said jack, there being an annular space between said sleeve and said jack which space is normally narrower than the radial dimension of said inturned ends of said fingers and said sleeve being of material which is sufliciently resilient to expand during assembly of the terminal to permit movement of said finger ends axially through said annular space and to contract to closely encircle and hold said finger ends in said annular recess when the terminal is assembled.

References Cited in the file of this patent UNITED STATES PATENTS 1,114,719 Beck Oct. 27, 1914 1,315,484 Fesler Sept. 9, 1919 1,401,217 Weiss Dec. 27, 1921 2,327,951 Zaleske Aug. 24, 1943 2,567,727 Quackenbush Sept. 11, 1951 FOREIGN PATENTS 105,227 Great Britain Feb. 14, 1918 

